Methods and Apparatus for Trapping and Accumulation of Ions

ABSTRACT

Methods and apparatus for ion accumulation are disclosed. An apparatus for ion accumulation includes multiple regions. A first region receives and transfers ions to a second region using a first drive potential. The second region is switchable between a first state where it generates a first electric field preventing ions from further movement and entering a third region, and a second state where it generates a second electric field that guides the ions toward the third region. When in the first state, the ions are prevented from further movement by the first electric field, which causes the ions to accumulate in the second region. When in the second state, the ions are moved from the second region to the third region by the second electric field. A method of accumulating ions involves switching an electric field applied to a region between a trap state and a release state.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of priority to U.S.Provisional Patent Application No. 63/028,768, filed on May 22, 2020,which is herein incorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates generally to the fields of ion mobilityspectrometry (IMS) and mass spectrometry (MS). More specifically, thepresent disclosure relates to methods and apparatus for trapping andaccumulation of ions to increase the resolution of ions in IMS and MSsystems.

RELATED ART

IMS is a technique for separating and identifying ions in the gaseousphase based on their mobilities. For example, IMS can be employed toseparate structural isomers and macromolecules that have differentmobilities. IMS relies on applying a constant or a time-varying electricfield to a mixture of ions within a static or dynamic background gas. Anion having a larger mobility (or smaller collision cross section [CCS])moves faster under the influence of the electric field compared to anion with a smaller mobility (or larger CCS). By applying the electricfield over a separation distance (e.g., in a drift tube) of an IMSdevice, ions from an ion mixture can be temporally or spatiallyseparated based on their mobility. Because ions with differentmobilities arrive at the end of the drift tube at different times(temporal separation) they can be identified based on the time ofdetection by a detector at the end of the drift tube. Resolution of themobility separation can be varied by changing the separation distance.

MS is an analytical technique that can separate a mixture of chemicalspecies based on their mass-to-charge ratio. MS involves ionizing themixture of chemical species followed by acceleration of the ion mixturein the presence of electric and/or magnetic fields. In some massspectrometers, ions having the same mass-to-charge ratio undergo thesame deflection or time dependent response. Ions with differentmass-to-charge ratios can undergo different deflections or timedependent response, and can be identified based on the spatial ortemporal position of detection by a detector (e.g., electronmultiplier).

IMS combined with MS can generate an IMS-MS spectrum that can be used ina broad range of applications, including metabolomics, glycomics, andproteomics. IMS-MS ion separation can be performed by coupling an ionmobility spectrometer with a mass spectrometer. For example, an ionmobility spectrometer can first separate the ions based on theirmobility. Ions having different mobilities can arrive at the massspectrometer at different times, and are then separated based on theirmass-to-charge ratio. One example of an IM spectrometer is a structurefor lossless ion manipulations (SLIM) device that can generate an IMSspectrum with minimal ion loss. SLIM devices can use traveling waveseparation as one technique to separate ions of different mobilities.However, traveling wave separation can result in broad peaks for ionmobility separations, particularly when the traveling wave separation isperformed over a long distance.

Moreover, the signal-to-noise ratio and resolution at the time ofdetection are impacted by the number of ions introduced into an IMSdevice. Accordingly, ion traps have been used to accumulate ions priorto injecting the ions for ion mobility separation, however, such iontraps are limited by space charge effects. In this regard, ion traps canaccumulate a limited number of charges before reaching space-chargecapacity, at which point ions can be lost from the trap. In the past,these limitations have generally been addressed by increasing the pathlength, which can result in a larger and/or more complex device.Additionally, systems and methods have been developed that impose anintermittent or “stuttering” traveling wave to sort, compress, orregroup ions into a reduced number of ion mobility bins, which resultsin ion spatial compression and increased resolution of ion packets inIMS. For example, U.S. Pat. No. 10,018,592 entitled Method and Apparatusfor Spatial Compression and Increased Mobility Resolution of Ions,discloses varying a duty cycle of an intermittent traveling wave tocompress ion packets into narrower distribution peaks. However, theforegoing methodology is still limited by the space charge effect andthe parameters (e.g., speed, amplitude, waveform, etc.) of the travelingwaves utilized.

Accordingly, there is a need for additional systems and methods foron-board trapping and accumulation of ions to increase the resolutionand sensitivity in IMS and MS systems.

SUMMARY

The present disclosure relates to methods and apparatus for on-boardtrapping and accumulation of ions to increase the resolution of ions inIMS and MS systems.

In accordance with embodiments of the present disclosure, exemplaryapparatus for ion accumulation are provided. An apparatus for ionaccumulation includes a first region and a second region. The firstregion is configured to receive ions and generate a first drivepotential configured to guide the ions across the first region in afirst direction. The second region is configured to receive the ionsfrom the first region, switch between a first state, which can be a trapstate, and a second state, which can be a release state, generate afirst electric field when in the first state, and generate a secondelectric field when in the second state. The first electric field isconfigured to prevent the ions from moving in the first direction andentering the third region, and the second electric field is configuredto guide the ions in the first direction toward a third region.Accordingly, the first electric field can be generated during the trapstate, and the second electric field can be generated during the releasestate. When the second region is in the first state, the first drivepotential and the first electric field prevent ions in the second regionfrom exiting the second region and cause the ions to accumulate in thesecond region. When the second region is in the second state, the secondelectric field causes the ions to move in the first direction toward thethird region.

In one aspect, the first drive potential can be a traveling wave. Inanother aspect, the first electric field can be a DC voltage. In suchaspects, the magnitude of the DC voltage can be greater than a voltagebias of the first drive potential. Additionally in such aspects, thesecond electric field can be a traveling wave, and the traveling wavecan be configured to separate the ions based on mobility. In otheraspects, a magnitude of the DC voltage can be less than a voltage biasof the first drive potential, and the DC voltage can create a potentialwell. In such aspects, the second electric field can be a DC potentialgradient or a traveling wave that can be configured to separate the ionsbased on mobility.

In some aspects, the first electric field can be a traveling wave thattravels in a second direction that is opposite to the first direction,and the second electric field can be a second traveling wave thattravels in the first direction. In such aspects, the second travelingwave can be configured to separate the ions based on mobility.Additionally, in such aspects, the first electric field can be generatedduring a trap state, and the second electric field can be generatedduring a release state.

In other aspects, the third region can be configured to receive the ionsfrom the second region and generate a second drive potential configuredto separate the ions based on mobility.

In still other aspects, the first region can include a plurality ofelectrodes disposed on a first surface, arranged along the firstdirection, and configured to generate the first drive potential, thesecond region can include one or more electrodes disposed on the firstsurface and arranged along the first direction, and at least one of theone or more electrodes of the second region can be configured togenerate the first electric field when in the first state and generatethe second electric field when in the second state.

In such aspects, the apparatus can include a controller that isconfigured to apply a first voltage signal to the plurality ofelectrodes of the first region, apply a second voltage signal to atleast one electrode of the one or more electrodes of the second region,and apply a third voltage signal to the at least one electrode of theone or more electrodes of the second region. Additionally, the pluralityof electrodes can be configured to generate the first drive potentialbased on the first voltage signal, the at least one electrode can beconfigured to generate the first electric field based on the secondvoltage signal, and the at least one electrode can be configured togenerate the second electric field based on the third voltage signal.When the apparatus is in a first mode of operation the controllerapplies the second voltage signal to the second plurality of electrodesplacing the second region in the first state, and when the apparatus isin a second mode of operation the controller applies the third voltagesignal to the second plurality of electrodes placing the second regionin the second state.

In some aspects, a first portion of the second region can generate thefirst electric field when the second region is in the first state, thefirst portion of the second region can generate the second electricfield when the second region is in the second state, and a secondportion of the second region can generate a fourth electric field thatis different than the first electric field.

In some other aspects, the second region can include a plurality of rowsof radio frequency (RF) electrodes and a plurality of traveling wave(TW) electrode arrays, and each of the plurality of TW electrode arrayscan include at least three individual electrodes. In such aspects, thefirst electric field can be generated by at least one of the individualelectrodes of each of the plurality of TW electrode arrays when thesecond region is in the first state.

A method for ion accumulation involves introducing ions into anapparatus for ion accumulation having a first region, a second region,and a third region. The method includes generating a drive potentialwithin the first region for guiding the ions across the first region ina first direction, and transferring the ions from the first region tothe second region with the drive potential. The method also includesgenerating a first electric field within the second region forpreventing the ions from moving in the first direction and entering thethird region, and accumulating ions in the second region. The firstelectric field can be applied during a trap state. The method furtherincludes switching the first electric field generated within the secondregion to a second electric field for guiding the accumulated ions inthe first direction toward the third region. The second electric fieldcan be generated during a release state.

In some aspects, the drive potential can be a traveling wave. In otheraspects, the first electric field can be a DC voltage. In such aspects,a magnitude of the DC voltage can be greater than a voltage bias of thedrive potential. In other such aspects, the second electric field can bea traveling wave, and the method can involve separating the ions basedon mobility with the traveling wave.

In other aspects, a magnitude of the DC voltage can be less than avoltage bias of the first drive potential, and the DC voltage can createa potential well. In such aspects, the second electric field can be a DCpotential gradient or a traveling wave. Where the second electric fieldis a traveling wave, the method can further involve separating the ionsbased on mobility with the traveling wave.

In still other aspects, the first electric field can be a firsttraveling wave that travels in a second direction that is opposite tothe first direction, and the second electric field can be a secondtraveling wave that travels in the first direction. In such aspects, themethod can further involve separating the ions based on mobility withthe traveling wave. Additionally, in such aspects, the first electricfield can be generated during a trap state, and the second electricfield can be generated during a release state.

In one aspect, the method can also involve transferring the ionsaccumulated in the second region to the third region, generated a seconddrive potential within the third region, and separating the ions basedon mobility with the second drive potential.

In some aspects, a first portion of the second region can generate thefirst electric field and the second electric field, and a second portionof the second region can generate a fourth electric field that isdifferent than the first electric field.

In some other aspects, the second region can include a plurality of rowsof radio frequency (RF) electrodes and a plurality of traveling wave(TW) electrode arrays, and each of the plurality of TW electrode arrayscan include at least three individual electrodes. In such aspects, thefirst electric field can be generated by at least one of the individualelectrodes of each of the plurality of TW electrode arrays when thesecond region is in the first state.

In another aspect, an apparatus for ion accumulation includes an ionchannel, a first region, a second region, a third region, and acontroller. The ion channel is defined between a first surface and asecond surface, extends along a first longitudinal direction and a firstlateral direction, and is configured to receive a stream of ions. Thefirst region includes a plurality of electrodes disposed on the firstsurface and arranged along the first longitudinal direction. The secondregion includes one or more electrodes disposed on the first surface andarranged along the first longitudinal direction. The controller isconfigured to apply a first voltage signal to the plurality ofelectrodes of the first region, apply a second voltage signal to the oneor more electrodes of the second region, and apply a third voltagesignal to the one or more electrodes of the second region. The secondvoltage signal can be applied during a trapping mode of operation, andthe third voltage signal can be applied during a release mode ofoperation. The plurality of electrodes of the first region areconfigured to generate, based on the first voltage signal, a first drivepotential that travels along the first longitudinal direction. The firstdrive potential is configured to guide the ions across the ion channelin the first longitudinal direction. The one or more electrodes of thesecond region are configured to generate, based on the second voltagesignal, a first electric field that prevents the ions from travelingalong the first longitudinal direction and into the third region. Thefirst electric field can be generated during the trapping mode ofoperation. The one or more electrodes of the second region areconfigured to generate, based on the third voltage signal, a secondelectric field configured to guide the ions along the first longitudinaldirection toward the third region. The third voltage signal can begenerated during the release mode of operation. When the apparatus is ina first mode of operation, which can be the trapping mode of operation,the controller applies the second voltage signal to the one or moreelectrodes of the second region, and the first drive potential and thefirst electric field prevent ions in the second region from exiting thesecond region, which causes the ions to accumulate in the second region.When the apparatus is in a second mode of operation, which can be therelease mode of operation, the controller applies the third voltagesignal to the one or more electrodes of the second region, and thesecond electric field causes the ions to move in the first directiontoward the third region.

In some aspects, the first voltage signal can be a traveling wave. Inother aspects, the second voltage signal can be a DC voltage. In suchaspects, a magnitude of the DC voltage can be greater than a voltagebias of the first drive potential. Also, in such aspects, the thirdvoltage signal can be a traveling wave, and the traveling wave can beconfigured to separate the ions based on mobility.

In other aspects, the second voltage signal can be applied to a singleelectrode of the second region.

In still other aspects, a magnitude of the DC voltage can be less than avoltage bias of the first drive potential, and the DC voltage can createa potential well. In such aspects, the third voltage signal can be a DCpotential gradient or a traveling wave that can be configured toseparate the ions based on mobility. In such aspects, the DC voltage canbe applied to two or more electrodes of the second region.

In one aspect, the second voltage signal can be a traveling wave thattravels in a second direction that is opposite to the first direction,and the third voltage signal can be a second traveling wave that travelsin the first direction. In such an aspect, the second traveling wave canbe configured to separate the ions based on mobility. Additionally, insuch aspects, the second voltage signal can be applied during a trappingmode of operation, and the third voltage signal can be applied during arelease mode of operation.

In another aspect, the third region can include a plurality ofelectrodes disposed on the first surface and arranged along the firstlongitudinal direction. The third region can be configured to receivethe ions from the second region and generate a second drive potentialconfigured to separate the ions based on mobility.

A method of ion accumulation involves introducing a stream of ions intoan ion channel of an ion accumulation device. The accumulation deviceincludes a first surface, a second surface, a first region including aplurality of electrodes disposed on the first surface and arranged alongthe first longitudinal direction, a second region including one or moreelectrodes disposed on the first surface and arranged along the firstlongitudinal direction, and a third region.

The first ion channel is defined between the first surface and thesecond surface, and extends along a first longitudinal direction and afirst lateral direction. The method also includes applying, by acontroller, a first voltage signal to the plurality of electrodes of thefirst region, and generating, by the plurality of electrodes of thefirst region, a first drive potential that travels along the firstlongitudinal direction. The first drive potential is also configured toguide the ions within the ion channel in the first longitudinaldirection. The method also includes transferring, with the first drivepotential, the ions within the ion channel from the first region to thesecond region along the first longitudinal direction. The method furtherincludes applying, by the controller, a second voltage signal to the oneor more electrodes of the second region, and generating, by the one ormore electrodes of the second region, a first electric field based onthe second voltage signal. The second voltage signal can be applied, andthe first electric field can be generated, during a trapping mode ofoperation. The method also includes preventing, with the first electricfield, the ions from moving in the first direction and entering thethird region, and accumulating ions in the second region. The methodfurther includes switching the second voltage signal applied to thesecond region by the controller to a third voltage signal for guidingthe ions accumulated in the second region within the ion channel in thefirst direction toward the third region. The third voltage signal can beapplied, and the second electric field can be generated, during arelease mode of operation.

In some aspects, the first voltage signal can be a traveling wave. Inother aspects, the second voltage signal can be a DC voltage. In suchaspects, a magnitude of the DC voltage can be greater than a voltagebias of the first voltage signal. In other such aspects, the thirdvoltage signal can be a traveling wave, and the method can involveseparating the ions based on mobility with the traveling wave. In stillother such aspects, the second voltage signal can be applied to a singleelectrode of the second region.

In other aspects, a magnitude of the DC voltage can be less than avoltage bias of the first voltage signal, and the DC voltage can createa potential well. In such aspects, the third voltage signal can be a DCpotential gradient or a traveling wave. Where the third voltage signalis a traveling wave, the method can further involve separating the ionsbased on mobility with the traveling wave. In such aspects, the DCvoltage can be applied to two or more electrodes of the second region.

In still other aspects, the second voltage signal can be a travelingwave that travels in a second direction that is opposite to the firstdirection, and the third voltage signal can be a second traveling wavethat travels in the first direction. In such aspects, the method canfurther involve separating the ions based on mobility with the travelingwave. Additionally, in such aspects, the second voltage signal can beapplied during a trapping mode of operation, and the third voltagesignal can be applied during a release mode of operation.

In one aspect, the method can also involve transferring the ionsaccumulated in the second region to the third region. This method canalso involve applying, by the controller, a fourth voltage signal to aplurality of electrodes of the third region, which can be disposed onthe first surface and arranged along the first longitudinal direction.This method can further involve generating, by the plurality ofelectrodes of the third region, a second drive potential that travelsalong the first longitudinal direction. The second drive potential canbe configured to guide the ions within the ion channel in the firstlongitudinal direction. This method can also involve separating the ionsbased on mobility with the second drive potential. In some aspects, thefourth voltage signal and the third voltage signal can be the same. Inother aspects, the first voltage signal, the third voltage signal, andthe fourth voltage signal can be the same.

An ion accumulation device includes an ion accumulation section, anoutlet section, and an outlet transition section. The ion accumulationsection has a first width and is configured to receive ions, switchbetween a first state and a second state, generate a first electricfield when in the first state, and generate a second electric field whenin the second state. The outlet section has a second width that is lessthan the first width and is configured to generate a third electricfield that is configured to guide the ions across the outlet section.The outlet transition section extends between the ion accumulationsection and the outlet section and has a tapering width that reducesfrom the first width adjacent the ion accumulation section to the secondwidth adjacent the outlet section. The outlet transition section is alsoconfigured to generate the third electric field to guide the ions acrossthe outlet transition section to the outlet section. The first electricfield is configured to prevent the ions from moving in a first directionand entering the outlet transition section, while the second electricfield is configured to guide the ions in the first direction toward theoutlet transition section. When the ion accumulation section is in thefirst state the first electric field prevents ions in the ionaccumulation section from exiting the ion accumulation section andcauses the ions to accumulate in the ion accumulation section. When theion accumulation section is in the second state the second electricfield causes the ions to move in the first direction toward the outlettransition section.

In some aspects, the outlet transition section can be configured toprevent ions from being discharged due to space charge effects. In someother aspects, the third electric field can be the same as the secondelectric field, or can be different than the second electric field.

In still other aspects, the ion accumulation device can also include aninlet section and an inlet transition section. The inlet section canhave a third width that is less than the first width, and the inlettransition section can extend between the inlet section and the ionaccumulation section. The inlet transition section can have a taperingwidth that increases from the third width adjacent the inlet section tothe first width adjacent the ion accumulation section. In such aspects,the inlet section and the outlet transition section can be configured togenerate a fourth electric field to guide the ions across the inletsection and the inlet transition section to the ion accumulationsection.

In some other aspects, the second electric field can be a traveling wavethat travels in the first direction, and the ion accumulation sectioncan be configured to be switched from generating the second electricfield to generating a fourth electric field that is a traveling wavethat travels in a second direction opposite the first direction.

In other aspects, the first electric field can be a DC voltage. In suchaspects, a first portion of the ion accumulation section can generatethe first electric field and a second portion of the ion accumulationsection can generate a fourth electric field that is different than thefirst electric field.

In still other aspects, the ion accumulation section can include aplurality of rows of radio frequency (RF) electrodes and a plurality oftraveling wave (TW) electrode arrays where each of the plurality of TWelectrode arrays includes at least three individual electrodes. In suchaspects, the first electric field can be generated by at least one ofthe individual electrodes of each of the plurality of TW electrodearrays.

In other aspects, the ion accumulation device can include an inletsection that is positioned at a lateral side of the ion accumulationsection and configured to provide ions to the ion accumulation section.

Other features will become apparent from the following detaileddescription considered in conjunction with the accompanying drawings. Itis to be understood, however, that the drawings are designed as anillustration only and not as a definition of the limits of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of the present disclosure will be apparent fromthe following Detailed Description of the Invention, taken in connectionwith the accompanying drawings, in which:

FIG. 1 is a schematic diagram of an exemplary ion mobility separation(IMS) system of the present disclosure;

FIG. 2 is a diagrammatic view of a portion of an exemplary SLIM devicethat can be used with the IMS system of FIG. 1 of the presentdisclosure;

FIG. 3 is a schematic diagram illustrating a first exemplary arrangementof electrodes on a surface of the SLIM device of FIG. 2 ;

FIG. 4 is a schematic diagram illustrating a second exemplaryarrangement of electrodes on a surface of the SLIM device of FIG. 2;

FIG. 5 is a block diagram showing exemplary regions of the SLIM deviceof FIG. 2;

FIG. 6 is a schematic and block diagram illustrating a first set ofexemplary waveforms applied to the exemplary regions of FIG. 5,including a high DC potential waveform for accumulating ions;

FIG. 7A is a schematic and block diagram illustrating a second set ofexemplary waveforms applied to the exemplary regions of FIG. 5 includinga DC potential well for accumulating ions and first release statewaveforms;

FIG. 7B is a schematic and block diagram illustrating the second set ofexemplary waveforms as shown in FIG. 7A, but with a second release statewaveform;

FIG. 8 is a schematic and block diagram illustrating a third set ofexemplary waveforms applied to the exemplary regions of FIG. 5,including opposing traveling waves for accumulating ions;

FIG. 9 is a block diagram illustrating an exemplary arrangement ofregions in an IMS system of the present disclosure for accumulating andseparating ions;

FIG. 10 is a schematic diagram of an exemplary accumulation region ofthe present disclosure; and

FIG. 11 is a schematic diagram of the exemplary accumulation region ofFIG. 10 with a lateral inlet section.

DETAILED DESCRIPTION

The present disclosure relates to methods and apparatus for on-boardtrapping and accumulation of ions, as described in detail below inconnection with FIGS. 1-11.

Ions can be separated based on their mobility via ion mobilityspectrometry (IMS). Mobility separation can be achieved, for example, byapplying one or more potential waveforms (e.g., traveling potentialwaveforms, direct current (DC) gradient, or both) on a collection ofions. IMS based mobility separation can be achieved by structures forlossless ion manipulation (SLIM) that can systematically apply travelingand/or DC potential waveforms to a collection of ions, such as thedevices disclosed and described in U.S. Pat. No. 8,835,839 entitled“Method and Apparatus for Ion Mobility Separations Utilizing AlternatingCurrent Waveforms” and U.S. Pat. No. 10,317,364 entitled “IonManipulation Device,” both of which are incorporated herein in theirentirety. This can result in a continuous stream of ions that aretemporally/spatially separated based on their mobility. In someimplementations, it can be desirable to select ions having apredetermined mobility range from a collection of ions. This can beachieved by mobility-based filtering of ions in SLIM devices (“SLIMfilters”). SLIM filters (e.g., low pass filters, high pass filters, bandpass filters, etc.) can apply a superposition to multiple potentialwaveforms that are directed (e.g., traveling) in different directions(e.g., in two-dimensions). Properties of the potential waveforms (e.g.,amplitude, shape, frequency, etc.) can determine the properties of theSLIM filter (e.g., bandwidth, cut-off mobility values, etc.).

The present disclosure utilizes the aforementioned SLIM devices to notonly transfer and separate ions of different mobilities, but to alsoaccumulate ions within the respective SLIM device for subsequentseparation and analysis. In this regard, different waveforms can beapplied to different regions of the SLIM device, e.g., one or moreelectrodes grouped together, to trap ions in an accumulation regionuntil the space-charge limit is reached or a sufficient number of ionsare accumulated, as discussed in greater detail below.

FIG. 1 is a schematic diagram of an exemplary ion mobility separation(IMS) system 100 in accordance with the present disclosure. The IMSsystem 100 includes an ionization source 102, a SLIM device 104, a massspectrometer 106, a controller 108, a computing device 110, a powersource 112, and a vacuum system 114. The ionization source 102 generatesions (e.g., ions having varying mobility and mass-to-charge-ratios) andinjects the ions into the SLIM device 104 (discussed in greater detailin connection with FIGS. 2-4). The SLIM device 104 can be configured totransfer ions, accumulate ions, store ions, and/or separate ions,depending on the desired functionality and waveforms applied thereto. Inthis regard, the SLIM device 104 can be used to select ions with one ormore predetermined ranges of mobility and direct the selected band (orbands) of ions to a detector, e.g., the mass spectrometer 106. Thevacuum system 114 can be in fluidic communication with the SLIM device104 and regulate the gas pressure within the SLIM device 104.Specifically, the vacuum system 114 can provide nitrogen to the SLIMdevice 104 while maintaining the pressure therein at a consistentpressure.

The SLIM device 104 can include one or more surfaces 114 a, 114 b (e.g.,printed circuit board surfaces) that can have a plurality of electrodesarranged thereon. The electrodes can receive voltage signals, a voltagewaveform, and/or a current waveform (e.g., a DC voltage or current, anRF voltage or current, or an AC voltage or current, or a superpositionthereof), and can generate a potential (e.g., a potential gradient) toconfine ions in the SLIM device 104, accumulate ions in the SLIM device104, and guide ions through the SLIM device 104, which can result in theaccumulation and separation of ions based on their mobility, asdiscussed in greater detail below.

The controller 108 can control operation of the ionization source 102,the SLIM device 104, the mass spectrometer 106, and the vacuum system114. For example, the controller 108 can control the rate of injectionof ions into the SLIM device 104 by the ionization source 102, thethreshold mobility of the SLIM device 104, and ion detection by the massspectrometer 106. The controller 108 can also control thecharacteristics and motion of potential waveforms generated by the SLIMdevice 104 (e.g., by applying RF/AC/DC potentials to the electrodes ofthe SLIM device 104) in order to transfer, accumulate, and/or separateions.

The controller 108 can control the properties of the potential waveforms(e.g., amplitude, shape, frequency, etc.) by varying the properties ofthe applied RF/AC/DC potential (or current). In this regard, thecontroller 108 can vary the properties of the potential waveforms fordifferent regions of the SLIM device 104, e.g., different groupings ofelectrodes, to trap/accumulate ions and subsequently separate ions. Thiscan be done in an effort to increase ion peak resolution, narrow ionpeaks, increase signal-to-noise ratio, and achieve sharp separationaround a targeted mobility.

The controller 108 can receive power from the power source 112, whichcan be, for example, a DC power source that provides DC voltage to thecontroller 108. The controller 108 can include multiple power supplymodules (e.g., current and/or voltage supply circuits) that generatevarious voltage (or current) signals that drive the electrodes of theSLIM device 104. For example, the controller 108 can include RF controlcircuits that generate RF voltage signals, traveling wave controlcircuits that generate traveling wave voltage signals, DC controlcircuits that generate DC voltage signals, etc. The RF voltage signals,traveling wave voltage signals, and DC voltage signals can be applied tothe electrodes of the SLIM device 104. The controller 108 can alsoinclude a master control circuit that can control the operation of theRF/traveling wave/DC control circuits. For example, the master controlcircuit can control the amplitude and/or phase of voltage (or current)signals generated by the RF/traveling wave/DC control circuits toachieve a desirable operation of the mobility filter system 100.

As discussed above, the SLIM device 104 can generate DC/travelingpotential waveforms (e.g., resulting from potentials generated bymultiple electrodes in the SLIM device 104) and DC potentials, which canperform mobility-based separations and cause ion accumulation. Thetraveling potential waveform can travel at a predetermined velocitybased on, for example, frequency of voltage signals applied to theelectrodes. In some implementations, the traveling potential waveformcan be spatially periodic and the spatial periodicity can depend on thephase differences between the voltage signals applied to adjacentelectrode pairs. In some implementations, the phase differences candetermine the direction of propagation of the potential waveform. Insome implementations, the waveform applied to accumulation/trapping/gateelectrodes can control accumulation of ions in the SLIM device 104. Themaster control circuit can control the frequency and/or phase of voltageoutputs of RF/traveling wave/DC control circuits such that the travelingpotential waveform has a desirable (e.g., predetermined) spatialperiodicity and/or speed, and the accumulation waveforms/potentialssufficiently restrict ion motion and thus accumulate ions.

In some implementations, the controller 108 can be communicativelycoupled to a computing device 110. For example, the computing device 110can provide operating parameters of the IMS system 100 via a controlsignal to the master control circuit. In some implementations, a usercan provide the computing device 110 (e.g., via a user interface) withthe operating parameters. Based on the operating parameters received viathe control signal, the master control circuit can control the operationof the RF/AC/DC control circuits which in turn can determine theoperation of the coupled SLIM device 104. In some implementations,RF/AC/DC control circuits can be physically distributed over the IMSsystem 100. For example, one or more of the RF/AC/DC control circuitscan be located in the IMS system 100, and the various RF/AC/DC controlcircuits can operate based on power from the power source 112.

FIG. 2 is a diagrammatic view of a portion of an exemplary SLIM device104 (e.g., SLIM device for transferring ions, accumulating ions, storingions, and or separating ions) that can be used with the IMS system 100of FIG. 1. The SLIM device 104 includes a first surface 114 a and asecond surface 114 b. The first and second surfaces 114 a, 114 b can bearranged (e.g., parallel to one another) to define one or more ionchannels there between. The first surface 114 a and the second surface114 b can include electrodes 116, 118 a-f, 120 a-e, 122 a-x (see FIGS. 3and 4), e.g., arranged as arrays of electrodes on the surfaces facingthe ion channel. The electrodes 116, 118 a-118 f, 120 a-e, 122 a-x onthe first surface 114 a and second surface 114 b can be electricallycoupled to the controller 108 and receive voltage (or current) signalsor waveforms therefrom. In some implementations, the first surface 114 aand second surface 114 b can include a backplane that includes multipleconductive channels that allow for electrical connection between thecontroller 108 and the electrodes 116, 118 a-f, 120 a-e, 122 a-x on thefirst surface 114 a and second surface 114 b. In some implementations,the number of conductive channels can be fewer than the number ofelectrodes 116, 118 a-f, 120 a-e, 122 a-x. In other words, multipleelectrodes 116, 118 a-f, 120 a-e, 122 a-x can be connected to a singleelectrical channel. As a result, a given voltage (or current) signal canbe transmitted to multiple electrodes 116, 118 a-f, 120 a-e, 122 a-xsimultaneously. Based on the received voltage (or current) signals, theelectrodes 116, 118 a-f, 120 a-e, 122 a-x can generate one or morepotentials (e.g., a superposition of various potentials) that canconfine, drive, and/or separate ions along a propagation axis (e.g.,z-axis).

FIG. 3 is a schematic diagram of the first and second surfaces 114 a,114 b of the SLIM device 104 illustrating a first exemplary arrangementof electrodes 116, 118 a-f, 120 a-e, 122 a-h thereon. The first andsecond surfaces 114 a, 114 b can be substantially mirror images relativeto a parallel plane, and thus it should be understood that thedescription of the first surface 114 a applies equally to the secondsurface 114 b, thus the second surface 114 b can include electrodes withsimilar electrode arrangement to the first surface 114 a.

The first surface 114 a includes guard electrodes 116, a plurality ofcontinuous electrodes 118 a-f, and a plurality of segmented electrodearrays 120 a-e. Each of the plurality of continuous electrodes 118 a-fcan receive voltage (or current) signals, or can be connected to groundpotential, and can generate a pseudopotential that can prevent orinhibit ions from approaching the first surface 114a. The plurality ofcontinuous electrodes 118 a-f can be rectangular in shape with thelonger edge of the rectangle arranged along the direction of propagationof ions undergoing mobility separation, e.g., along the propagation axiswhich is parallel to the z-axis shown in FIG. 3. The plurality ofcontinuous electrodes 118 a-f can be separated from each other along alateral direction, e.g., along the y-axis, which can be perpendicular tothe direction of propagation, e.g., the z-axis.

Each of the plurality of segmented electrode arrays 120 a-e can beplaced between two continuous electrodes 118 a-f, and includes aplurality of individual electrodes 122 a-h, e.g., eight electrodes,sixteen electrodes, twenty-four electrodes, etc., that are arrangedalong (parallel to) the direction of propagation, e.g., along thez-axis. It should be understood that each segmented electrode array 120a-e can include more or less than eight electrodes, but should includeat least three electrodes. For example, as shown in FIG. 4, thesegmented electrode arrays 120 a-e each include twenty-four electrodes122 a-x. Additionally, the individual electrodes 122 a-x can beseparated into individual groups that receive specific signals from thecontroller 108, discussed in greater detail below. The plurality ofsegmented electrode arrays 120 a-e can receive a second voltage signaland generate a drive potential that can drive ions along the propagationaxis or a DC voltage signal that can trap ions, which is discussed ingreater detail below. That is, the first and second surfaces 114 a, 114b, and the electrode arrangements thereof, can be implemented fordifferent purposes, and thus have different functionalities, based uponthe voltage settings applied to the continuous electrodes 118 a-f, thesegmented electrode arrays 120 a-e, and the plurality of individualelectrodes 122 a-h.

The plurality of continuous electrodes 118 a-f and the plurality ofsegmented electrode arrays 120 a-e can be arranged in alternatingfashion on the first surface 114 a between the DC guard electrodes 116.The segmented electrodes 120 a-e can be traveling wave (TW) electrodessuch that each of the individual electrodes 122 a-h of each segmentedelectrode array 120 a-e receives a voltage signal that is simultaneouslyapplied to all individual electrodes 122 a-h, but phase shifted betweenadjacent electrodes 122 a-h along the z-axis. However, the sameindividual electrodes, e.g., the first individual electrodes 122 a, ofthe segmented electrode arrays 120 a-e receive the same voltage signalwithout phase shifting.

The voltage signal applied to the individual electrodes 122 a-h can be asinusoidal waveform (e.g., an AC voltage waveform), a rectangularwaveform, a DC square waveform, a sawtooth waveform, a biased sinusoidalwaveform, a pulsed current waveform, etc., and the amplitude of thesignal provided to the individual electrodes 122 a-h can be determinedbased on the voltage waveform applied, e.g., in view of the phaseshifting referenced above. For example, if a single wavelength of an ACvoltage waveform extends over eight electrodes (e.g., the individualelectrodes 122 a-h), then amplitudes of the voltage signals applied tothe individual electrodes 122 a-h can be determined by selecting valuesfrom the AC waveform for phase shifts corresponding to the total numberof electrodes (e.g., eight electrodes) associated with a singlewavelength. For example, the phase shift between adjacent electrodes ofthe individual electrodes 122 a-h is 45 degrees (360 degrees of a singlewavelength cycle divided by 8). This can be achieved by electricallycoupling the individual electrodes 122 a-h to different traveling wavecontrol circuits, e.g., AC control circuits, DC (square wave) controlcircuits, pulsed current control circuits, etc., that generate voltagesignals that are phase shifted with respect to each other.Alternatively, the controller 108 could be a single traveling wavecontrol circuit that can generate voltage signals that can besimultaneously applied to the electrodes 122 a-h. It should beunderstood that the voltage or current waveform can take various forms,e.g., square, triangular, rectangular, sawtooth, etc., can be periodic,can be aperiodic, etc. For example, the controller 108 could be atraveling wave control circuit that can include one or more DC (squarewave) control circuits that generate DC voltage signals and AC controlcircuits that generate sinusoidal signals.

As noted above, the controller 108 can include one or more pulsedvoltage or current control circuits that can generate a pulsed voltage(or current) waveform, e.g., square, triangular, rectangular, sawtooth,etc. The pulsed voltage (or current) waveform can be periodic with nopolarity reversal. The pulsed voltage (or current) control circuits caninclude multiple outputs that are electrically connected to theindividual electrodes 122 a-h. In some implementations, the controller108 can be a pulsed voltage (or current) control circuit that cansimultaneously apply multiple voltage signals (e.g., that constitute thepulsed waveform) to each of the individual electrodes 122 a-h. Thevarious pulse shapes of the voltage (or current) waveform can begenerated by a superposition of DC voltage signals and sinusoidalsignals. The controller 108 can determine the phase shift between thevoltage signals generated by the various traveling wave controlcircuits. The shape/periodicity of the traveling potential waveform canbe based on the phase shift between the voltage signals applied toadjacent electrodes 122 a-h. The controller 108 can determine theamplitudes of the DC voltage signals generated by DC control circuits,and can determine the amplitude and/or frequency of the AC signalgenerated by the traveling wave control circuits.

The frequency of the voltage signals (e.g., AC signal) can determine thespeed of the traveling potential waveform. An alternate approach togenerating phase shifted AC signals for the voltage (or current)waveform, which generates the traveling potential waveform, is the useof multiphase transformers. This approach can provide control of thephase relationships between multiple voltage output signals based uponthe connection scheme of the multiple secondary windings of thetransformer. In this way, one or more input drive voltage(s) signal canbe used to generate multiple phase dependent outputs with only analogcircuitry. A key differentiation between this approach and the digitalgeneration methods described above is the fact that the phase dependencecan be dictated by the physical wiring of the transformer and may not bechanged without making a physical change to the wiring. The phaserelationships between digitally generated waveforms can be dynamicallyvaried without a change in hardware.

As time progresses, the potential waveform (e.g., generated by ACwaveform, sinusoidal voltage waveform, pulsed voltage [or current]waveform applied to the electrodes) can travel along the direction ofpropagation, e.g., along the z-axis. This can result in a change in theamplitude of the voltage applied to the individual electrodes 122 a-h.For example, the voltage applied to the first individual electrode 122 aduring a first time step is applied to the adjacent individual electrode122 b during the next time step. The controller 108 can include one ormore traveling wave control circuits that can generate the pulsedvoltage/current waveform, AC waveform, etc. In some implementations, thecontroller can include one or more RF control circuits that can generatean RF voltage waveform, discussed in greater detail below.

The controller 108 can control the speed of the traveling potentialwaveform by controlling the frequency and/or phase of the AC/RF/pulsedvoltage (or current) waveform applied to the individual electrodes 122a-h. As the potential waveform travels, ions introduced into the SLIMdevice 104 can be pushed along the direction of propagation andpotentially separated along the z-axis based on their mobility, ifdesired. In this regard, the traveling waveform applied by thecontroller 108 can be used to transfer the ions without separating themor transfer the ions and separate them during the transfer based onmobility.

As noted above, the plurality of continuous electrodes 118 a-f can beconnected to one or more voltage control circuits, e.g., voltage controlcircuits in the controller 108, and receive RF signals therefrom. The RFvoltages applied to the continuous electrodes 118 a-f can be phaseshifted with respect to adjacent continuous electrodes 118 a-f. That is,adjacent continuous electrodes 118 a-f can receive the same RF signal,but phase shifted by 180 degrees. Accordingly, in a first state, thefirst, third, and fifth electrodes 118 a, 118 c, 118 e can have apositive polarity (indicated as RF+) while the second, fourth, and sixthcontinuous electrodes 118 b, 118 d, 118 f can have a negative polarity(indicated as RF−). As time and the signal advances, the polarity ofeach of the continuous electrodes 118 a-f switches. The foregoingfunctionality retains the ions between the first and second surfaces 114a, 114 b and prevents the ions from contacting the first and secondsurfaces 114 a, 114 b.

As noted above, the SLIM device 104 can have more or less than eightindividual electrodes 122 a-h in each of the segmented electrode arrays120 a-e, and can include more or less than five segmented electrodearrays 120 a-e and six continuous electrodes 118 a-f depending on thefunctionality desired of the SLIM device 104. For example, FIG. 4 is aschematic diagram of the first and second surfaces 114 a, 114 b of theSLIM device 104 illustrating second and third exemplary arrangement ofelectrodes 116, 118 a-f, 120 a-e, 122 a-x thereon. More specifically,the arrangement of electrodes 116, 118 a-f, 120 a-e, 122 a-x shown inFIG. 4 is substantially the same as the arrangement shown in FIG. 3, butwith twenty-four individual electrodes 122 a-x for each of the segmentedelectrode arrays 120 a-e, the six continuous electrodes 118 a-f brokeninto sets of three, and the guard electrodes 116 broken into sets ofthree.

In this configuration, the first set of eight individual electrodes 122a-h can be used for a first function, e.g., to transfer ions with orwithout separating them, the second set of eight individual electrodes122 i-p can be used for a second function, e.g., to trap and accumulateions, and the third set of eight individual electrodes 122 q-x can beused for a third function, e.g., to separate ions while transferringthem. For example, the controller 108 can provide a first waveform tothe first set of eight individual electrodes 122 a-h, a second waveformto the second set of eight individual electrodes 122 i-p, and a thirdwaveform to the third set of eight individual electrodes 122 q-x.Additionally, each of the individual electrodes 122 a-x can beindividually controlled by the controller 108 and provided with awaveform or voltage (e.g., DC voltage value), or switched betweendifferent waveforms or voltages, depending on desired functionality.

Accordingly, the individual electrodes 122 a-x can be divided intogroups as necessary and according to design considerations.

As shown in FIG. 5, which is a block diagram showing exemplary regionsof the SLIM device 104 of FIG. 2, the individual electrodes 122 a-x canbe grouped into the different regions based on their desiredfunctionality. For example, the SLIM device 104 can include a transferregion 124, an accumulation region 126, and a separation region 128. Thetransfer region 124 can have a traveling wave applied thereto whichtransfers ions to the accumulation region 126. The accumulation region126 can trap and accumulate ions, e.g., through the implementation ofone or more switching/gate electrodes. The separation region 128 canseparate and transfer ions once released from the accumulation region126. The electrode arrangement illustrated in FIG. 3 can be implementedin any of the transfer, accumulation, and separation regions 124, 126,128, with the voltages being applied to the respective electrodesdictating the functionality. For example, the first set of eightindividual electrodes 122 a-h of FIG. 4 can be implemented as thetransfer region 124, the second set of eight individual electrodes 122i-p of FIG. 4 can be implemented as the accumulation region 126, and thethird set of eight individual electrodes 122 q-x of FIG. 4 can beimplemented as the separation region 128.

Additionally, as shown in FIGS. 4 and 5, the accumulation region 126 canbe provided with separate sets of continuous electrodes 118 a-f andseparate sets of guard electrodes 116, which can be individuallycontrolled and have different voltages applied thereto by the controller108. This configuration allows for a different RF and DC voltages to beapplied to the accumulation region 126. For example, the amplitude ofthe RF voltage applied to the continuous electrodes 118 a-f in theaccumulation region 126 can be reduced to avoid exciting the ions, andthe RF voltage applied to the continuous electrodes 118 a-f in theaccumulation region 126 and the DC guard voltage applied to the guardelectrodes 116 in the accumulation region 126 can be adjusted to matchthe voltage applied to the second set of individual electrodes 122 i-pof the accumulation region 126.

FIG. 6 is a schematic and block diagram illustrating a first set ofexemplary waveforms applied to the regions 124, 126, 128 of the SLIMdevice 104, and exemplary ion motion through the regions 124, 126, 128.The transfer region 124 has a first traveling wave 130 applied thereto,which transfers the ions 132 a-c along the propagation axis, e.g., thez-axis, and to the accumulation region 126. The first traveling wave 130can be generated by the controller 108, and can be customized so as totransfer the ions 132 a-c with or without separating the ions 132 a-cbased on mobility. The transfer region 124 can comprise a plurality ofthe individual electrodes 122 a-x of each segmented electrode array 120a-e. For example, the first through eighth individual electrodes 122 a-hfor all segmented electrode arrays 120 a-e can receive the firsttraveling wave 130 and transfer the ions 132 a-c to the accumulationregion 126. The accumulation region 126 can partially overlap thetransfer region 124 in that the first traveling wave 130 extends intothe accumulation region 126.

The accumulation region 126 can have two different states/modes ofoperation, e.g., a trap state and a release state, that it can operatein for different periods of time. When in the trap state/mode ofoperation, the first traveling wave 130 can extend into the accumulationregion 126 and a single gate electrode 131, e.g., the first individualelectrode 122 a of each segmented electrode array 120 a-e in theseparation region 128 (for example, the seventeenth individual electrode122 q of FIG. 4) or the eighth individual electrode 122 h of eachsegmented electrode array 120 a-e in the accumulation region 126 (forexample, the sixteenth individual electrode 122 p of FIG. 4), can havethe signal applied thereto switched from the first traveling wave 130 toa signal configured to trap or prevent the ions 132 a-c from continuedpropagation. More specifically, the gate electrode receives a high DCpotential voltage signal 134 from the controller 108 that is greater inpotential than the voltage bias of the first traveling wave 130. Thevoltage bias of the first traveling wave 130 is generally a fixed DCvoltage applied to the first traveling wave 130 to shift the waveform.As such, the first traveling wave 130 continuously transfers ions 132a-c provided to the SLIM device 104, e.g., from the ionization source102, along the propagation axis until the ions 132 a-c reach the gateelectrode 131 where they are stopped, e.g., repelled, by the high DCpotential voltage signal 134. Nonetheless, the continuously cyclingfirst traveling wave 130 prevents the ions 132 a-c from propagating inthe opposite direction, e.g., in the negative z-axis direction, andinstead traps the ions 132 a-c against the high DC potential voltagesignal 134 by continuously pushing the ions 132 a-c in the propagationdirection, e.g., the positive z-axis direction, which allows for theions 132 a-c to accumulate in the accumulation region 126. Thisessentially packetizes the ions 132 a-c so that they can be collectivelyseparated in the separation region 128.

Accordingly, in operation, ions 132 a-c can be continuously fed to theSLIM device 104 when in the trap state/mode of operation until asufficient number of ions have been accumulated, which can be determinedby whether the space charge limit has been reached. More specifically,space charge effects limit the maximum number of charges that can becontained within a given length before ions are discharged. Generally,there is a space charge limit of approximately one million charges perone millimeter of path length in the SLIM device 104. Accordingly, if asingle traveling wave segment, e.g., the electrode segment shown in anddescribed in connection with FIG. 3 that includes six RF electrodes 118a-f and five segmented electrode arrays 120 a-e having eight individualelectrodes 122 a-h, is used for accumulating ions and that segment is,for example, nine millimeters in length, then the space charge limit(e.g., accumulation capacity) is approximately nine million charges.That is, nine million charges can be accumulated before the space chargelimit is exceed, at which point ions can be lost from the trap. It isnoted that the space charge limit is based on the total charge value ofall ions accumulated, and not the number of ions. For example, some ionsmay have a greater charge value, e.g., +40 or +50, and in suchcircumstances fewer ions would be accumulated than if ions having +10charge were accumulated. Moreover, the foregoing assumes a singletraveling wave segment having six RF electrodes 118 a-118 f and fivesegmented electrode arrays 120 a-e, however, additional rows can beadded to increase the accumulation capacity per unit length ifadditional capacity is required, e.g., in order to increase thesensitivity of the analysis. For example, a sixth segmented electrodearray and an eighth continuous RF electrode could be added to theelectrode configuration shown in FIG. 3 and FIG. 4, which would provideadditional space for ion accumulation.

The gate electrode 131 can be a switchable electrode such that it canoperate in the trap state for a first period of time until a sufficientnumber of ions have been accumulated, the signal applied thereto canthen be switched to a release state, which the gate electrode 131 canoperate in for a second period of time. For example, the signal can beswitched from the high DC potential voltage signal 134 to a secondtraveling wave 136 so that it is in sync with the second traveling wave136 applied to the separation region 128, which will cause theaccumulated ions 132 a-c to be released into the separation region 128.The second traveling wave 136, which can be generated by the controller108, is applied to the electrodes of the separation region 128, andseparates the ions 132 a-c along the z-axis based on their mobility andpushes the ions 132 a-c along the direction of propagation, e.g., thez-axis, toward the mass spectrometer 106 for analyzing. The separationregion 128 can comprise a plurality of the individual electrodes 122 a-xof each segmented electrode array 120 a-e. For example, the seventeenththrough twenty-fourth individual electrodes 122 q-x for all segmentedelectrode arrays 120 a-e (see FIG. 4) can receive the second travelingwave 136. It is noted that the transfer region 124 can also function asa separation region such that the first traveling wave 130 is the sameas the second traveling wave 136, which can assist with syncing thefirst and second traveling waves 130, 136 when switching between thetrap state/mode of operation and the release state/mode of operation.

FIG. 7A is a schematic and block diagram illustrating a second set ofexemplary waveforms applied to the regions 124, 126, 128 of the SLIMdevice 104 and exemplary ion motion through the regions 124, 126, 128,including first release state waveforms (release states lA and 1B). FIG.7B is a schematic and block diagram illustrating the second set ofexemplary waveforms as shown in FIG. 7A, but with a second release statewaveform.

The first traveling wave 130 is applied to the transfer region 124, asdescribed above, and transfers the ions 132 a-c along the propagationaxis, e.g., the z-axis, and to the accumulation region 126. The firsttraveling wave 130 can be generated by the controller 108, and can becustomized so as to transfer the ions 132 a-c with or without separatingthe ions 132 a-c based on mobility. The transfer region 124 can comprisea plurality of the individual electrodes 122 a-x of each segmentedelectrode array 120 a-e. For example, the first through eighthindividual electrodes 122 a-h for all segmented electrode arrays 120 a-ecan receive the first traveling wave 130 and transfer the ions 132 a-cto the accumulation region 126. The accumulation region 126 canpartially overlap the transfer region in that the first traveling wave130 extends into the accumulation region 126.

The accumulation region 126 can have two different states/modes ofoperation, e.g., a trap state/mode of operation and a release state/modeof operation, that it can operate in for different periods of time. Whenin the trap state/mode of operation, the first traveling wave 130 canextend into the accumulation region 126 and plurality of gate/trapelectrodes can have the signal applied thereto switched from the firsttraveling wave 130 to a signal configured to trap or prevent the ions132 a-c from continued propagation. For example, a couple of electrodescould be implemented as gate/trap electrodes, such as the first andsecond individual electrodes 122 a, 122 b of each segmented electrodearray 120 a-e (see FIG. 3) in the accumulation region 126 (e.g., theninth and tenth individual electrodes 122 i, 122 j of FIG. 4) or theseventh and eighth individual electrodes 122 g, 122 h of each segmentedelectrode array 120 a-e (see FIG. 3) in the accumulation region 126(e.g., the fifteenth and sixteenth individual electrodes 122 o, 122 p ofFIG. 4), or the entire array of individual electrodes 122 a-h of eachsegmented electrode array 120 a-e (see FIG. 3) in the accumulationregion 126 (e.g., the ninth through sixteenth individual electrodes 122i-p of FIG. 4) could be implemented as gate/trap electrodes.

More specifically, the gate/trap electrodes (e.g., the seventh andeighth electrodes 122 g, 122 h) receive a low DC potential voltagesignal 140 from the controller 108 for a first period of time, whichcreates a potential well (e.g., a DC potential well) that is lower inpotential than the voltage bias of the first traveling wave 130 and thesecond traveling wave 142 of the separation region 128. As such, thefirst traveling wave 130 continuously transfers ions 132 a-c provided tothe SLIM device 104, e.g., from the ionization source 102, along thepropagation axis until the ions 132 a-c reach the gate/trap electrodes122 g, 122 h where they are trapped as they are unable to overcome thepotential of the second traveling wave 142 in the separation region 128.Similarly, the continuously cycling first traveling wave 130 preventsthe ions 132 a-c from propagating in the opposite direction, e.g., inthe negative z-axis direction, and traps the ions 132 a-c within the lowpotential well 140, which causes the ions 132 a-c to accumulate in theaccumulation region 126, e.g., within the low potential well 140. Thisessentially packetizes the ions 132 a-c so that they can be collectivelyseparated in the separation region 128.

Accordingly, in operation, ions 132 a-c can be continuously fed to theSLIM device 104 when in the trap state/mode of operation until asufficient number of ions have been accumulated in the low potentialwell 140 and the accumulation region 126, which, as discussed above, canbe determined by whether the space charge limit has been reached.However, since the accumulation region 126, e.g., the low potential well140, extends across a plurality of electrodes, the capacity of the trapcan be controlled, as more than two electrodes can be used to create thelow potential well in order to accumulate a greater number of ioncharges. Moreover, additional rows can be added to increase theaccumulation capacity per unit length if additional capacity isrequired, e.g., in order to increase the sensitivity of the analysis.For example, a sixth segmented electrode array and an eighth continuousRF electrode could be added to the electrode configuration shown inFIGS. 3 and 4, which would provide additional space for ionaccumulation.

The gate/trap electrodes 122 g, 122 h can be switchable electrodes suchthat once a sufficient number of ions have been accumulated, the signalapplied thereto can be switched into a release state. For example, asshown by release state 1A in FIG. 7A, the signal applied to thegate/trap electrodes 122 g, 122 h can be switched from the low DCpotential voltage signal 140 to a ramped DC potential voltage signal 144(e.g., a DC potential gradient) that decreases in potential and travelsacross the gate/trap electrodes 122 g, 122 h to push theaccumulated/trapped ions 132 a-c toward the separation region 128, whichcauses the accumulated ions 132 a-c to be released into the separationregion 128. The second traveling wave 142, which can be generated by thecontroller 108, is applied to the separation region 128 and isconfigured to interface or sync with the ramped DC potential voltagesignal 144 such that the ions 132 a-c are transferred from theaccumulation region 126 to the separation region 128 for propagation andseparation. The second traveling wave 142 separates the ions 132 a-calong the z-axis based on their mobility and pushes the ions 132 a-calong the direction of propagation, e.g., the z-axis, toward the massspectrometer 106 for analyzing. The separation region 128 can comprise aplurality of the individual electrodes 122 a-x of each segmentedelectrode array 120 a-e. For example, the seventeenth throughtwenty-fourth individual electrodes 122 q-x for all segmented electrodearrays 120 a-e (see FIG. 4) can receive the second traveling wave 142.It is noted that the transfer region 124 can also function as aseparation region such that the first traveling wave 130 is the same asthe second traveling wave 136.

Alternatively, as shown by release state 1B in FIG. 7A, the secondtraveling wave 142 can be offset from the first traveling wave 130,e.g., a lower voltage bias can be applied to the second traveling wave142 than to the first traveling wave 130. In this configuration, the DCpotential voltage signal 140 could be configured to ramp down from thevoltage bias of the first traveling wave 130 to the voltage bias of thesecond traveling wave 142 to transition and push the ions 132 a-132 cfrom the accumulation region 126 to the separation region 128 forpropagation and separation.

Alternative to implementing the ramped DC potential voltage signal 144during a release state/mode, the controller 108 can provide a thirdtraveling wave 146 to the gate/trap electrodes 122 g, 122 h when in therelease state/mode, as shown in FIG. 7B, which illustrates the secondrelease state waveform. That is, the signal provided to the gate/trapelectrodes 122 g, 122 h can be switched from the low DC potentialvoltage signal 140 to the third traveling wave 146, which can beconfigured to interface or sync with the first traveling wave 130 and/orthe second traveling wave 142 so that it pushes the accumulated/trappedions 132 a-c toward and into the separation region 128 where the secondtraveling wave 142 is applied. The second traveling wave 142 can begenerated by the controller 108 and configured to interface or sync withthe third traveling wave 146 such that the ions 132 a-c are transferredfrom the accumulation region 126 to the separation region 128 forpropagation and separation, as discussed above.

Additionally, as noted in connection with FIG. 4 the accumulation region126 can be provided with separate sets of continuous electrodes 118 a-fand separate sets of guard electrodes 116, which can be individuallycontrolled and have different voltages applied thereto by the controller108. This configuration allows for a different RF and DC voltages to beapplied to the accumulation region 126. For example, when theaccumulation 126 is in a trap state, and thus receiving a low DCpotential voltage signal 140, the amplitude of the RF voltage applied tothe continuous electrodes 118 a-f in the accumulation region 126 can bereduced to avoid exciting the ions, and the DC guard voltage applied tothe guard electrodes 116 in the accumulation region 126 can be reducedto match the voltage applied to the individual electrodes 122 i-p of theaccumulation region 126, but maintained at a level to ensure that ionsdo not exit from the sides. Additionally, the RF voltage applied to thecontinuous electrodes 118 a-f and the DC guard voltage applied to theguard electrodes 116 can adjusted when the accumulation region 126 isswitched to the release state, which involves a change in voltage signalapplied to the individual electrodes 122 i-p. For example, if thevoltage signal applied to the individual electrodes 122 i-p is increasedduring a release state, then the DC guard voltage applied to the guardelectrodes 116 can be increased to ensure that ions do not escape fromthe sides of the SLIM device 104.

FIG. 8 is a schematic and block diagram illustrating a third set ofexemplary waveforms applied to the exemplary regions 124, 126, 128 ofthe SLIM device 104 and exemplary ion motion through the regions 124,126, 128. In particular, FIG. 8 demonstrates the implementation ofopposed traveling waves used to trap and accumulate ions. The firsttraveling wave 130 is applied to the transfer region 124, as describedabove, and transfers the ions 132 a-c along the propagation axis, e.g.,the z-axis, and to the accumulation region 126. The first traveling wave130 can be generated by the controller 108, and can be customized so asto transfer the ions 132 a-c with or without separating the ions 132 a-cbased on mobility. The transfer region 124 can comprise a plurality ofthe individual electrodes 122 a-x of each segmented electrode array 120a-e. For example, the first through eighth individual electrodes 122 a-hfor all segmented electrode arrays 120 a-e can receive the firsttraveling wave 130 and transfer the ions 132 a-c to the accumulationregion 126.

Similarly, the separation region 128 can have a second traveling wave142 applied thereto, which can be generated by the controller 108. Theseparation region 128 can comprise a plurality of the individualelectrodes 122 a-x of each segmented electrode array 120 a-e. Forexample, the seventeenth through twenty-fourth individual electrodes 122q-x for all segmented electrode arrays 120 a-e (see FIG. 4) can receivethe second traveling wave 142. Thus, the second traveling wave 142 canstart where the first traveling wave 130 ends. In this regard, thesecond traveling wave 142 can be the same waveform as the firsttraveling wave 130 such that they essentially form a single continuouswave.

However, the SLIM device 104 can have two different states/modes ofoperation, e.g., a trap state/mode of operation and a release state/modeof operation, that it operates in for different periods of time. When inthe trap state/mode of operation, the controller 108 can apply a thirdtraveling wave 148 to the separation region for a period of time, e.g.,to the seventeenth through twenty-fourth individual electrodes 122 q-x,that travels in the opposite direction of the first traveling wave 130,e.g., toward the first traveling wave 130 along the negative directionof the z-axis. Accordingly, the first traveling wave 130 and the thirdtraveling wave 148 can be opposing waves that meet at the accumulationregion 126. Additionally, the third traveling wave 148 can have the samefrequency and magnitude as the first traveling wave 124, but propagatein the opposite direction. In this configuration, the individualelectrodes 122 q-x of the separation region can be switchable such thatduring the trap state/mode of operation the controller 108 applies thethird traveling wave 148 thereto and in a release state/mode ofoperation applies the second traveling wave 142 thereto.

As such, when the SLIM device 104 is operated in the trap state/mode ofoperation, the first traveling wave 130 continuously transfers ions 132a-c provided to the SLIM device 104, e.g., from the ionization source102, along the propagation axis until the ions 132 a-c reach theaccumulation region 126, e.g., the point between the eighth electrode122 h and the ninth electrode 122 i, where they are stopped due to theopposing first and third traveling waves 130, 148. That is, while thefirst traveling wave 130 pushes the ions 132 a-c along the positivedirection of the z-axis, the second traveling wave 148 pushes the ions132 a-c in the opposite direction in the negative direction of thez-axis. Thus, the continuously cycling third traveling wave 148 preventsthe ions 132 a-c from further propagating along the z-axis and acrossthe SLIM device 104, and the continuously cycling first traveling wave130 transfers the ions 132 a-c to the accumulation region 126 andsubsequently prevents the ions 132 a-c from propagating in the oppositedirection, e.g., along the z-axis in the negative direction. Theopposing first and third traveling waves 130, 148 prevent the ions 132a-c located in the accumulation region 126 from traveling anysignificant distance along the z-axis, and thus trap the ions 132 a-cand allow the ions 132 a-c to accumulate in the accumulation region 126.This essentially packetizes the ions 132 a-c so that they can becollectively separated in the separation region 128.

Accordingly, in operation, ions 132 a-c can be continuously fed to theSLIM device 104 when in the trap state/mode of operation until asufficient number of ions have been accumulated in the accumulationregion 126, which, as discussed above, can be determined by whether thespace charge limit has been reached. Moreover, additional rows can beadded to increase the accumulation capacity per unit length ifadditional capacity is required, e.g., in order to increase thesensitivity of the analysis. For example, a sixth segmented electrodearray and an eighth continuous RF electrode could be added to theelectrode configuration shown in FIGS. 3 and 4, which would provideadditional space for ion accumulation.

As previously noted, the separation region electrodes 122 q-x can beswitchable electrodes such that once a sufficient number of ions havebeen accumulated, the signal applied thereto can be switched into arelease state. For example, the signal can be switched from the thirdtraveling wave 148 to the second traveling wave 142 in sync with thefirst traveling wave 130 applied to the transfer region, which causesthe accumulated ions 132 a-c to be released into the separation region128. The second traveling wave 136, which can be generated by thecontroller 108, is applied to the separation region 128, and separatesthe ions 132 a-c along the z-axis based on their mobility and pushes theions 132 a-c along the direction of propagation, e.g., the z-axis,toward the mass spectrometer 106 for detection. It is noted that thetransfer region 124 can also function as a separation region such thatthe first traveling wave 130 is the same as the second traveling wave136, which can assist with syncing the first and second traveling waves130, 136 when switching between the trap state/mode of operation and therelease state/mode of operation.

FIG. 9 is a block diagram illustrating an exemplary arrangement oftransfer, accumulation, and separation regions 124, 126, 128 in the IMSsystem 100 of the present disclosure for accumulating and separatingions. As shown in FIG. 9, the IMS system 100 can include a plurality oftransfer regions 124, accumulation regions 126, and separation regions128 in order to further increase the resolution. It is noted thatalternative arrangements and configurations are contemplated by thepresent disclosure. In this regard, it is noted that it is not necessarythat the different regions 124, 126, 128 be placed in a straight line.Instead, for example, the transfer region 124 may be placedperpendicular to the accumulation or separation regions 126, 128.Additionally, gates can be implemented with the present disclosure inorder to, for example, control the flow of ions from the transfer region124 to the accumulation region 126, or from the separation region 128 toa second accumulation region 126.

FIG. 10 is a schematic diagram of an exemplary accumulation region 150of the present disclosure, which can be implemented, for example, as theaccumulation region 126 shown and described in connection with FIGS.5-9. That is, it should be understood that the description of theaccumulation region 126 and functionality thereof is equally applicableto the accumulation region 150 illustrated in FIG. 10, including theabove-described applied waveforms, trap states, and release states.

The accumulation region 150 includes an inlet section 152, an inlettransition section 154, an ion accumulation section 156, an outlettransition section 158, and an outlet section 160. Each of the sections150-160 generally includes a plurality of rows of continuous electrodes162 and a plurality of segmented electrode arrays 164, the number ofwhich can vary between sections 150-160, as discussed in greater detailbelow. In this regard, some of the rows of continuous electrodes 162 andsegmented electrode arrays 164 can extend through more than one section150-160 with some extending through all sections 150-160 of theaccumulation region 150, as shown in FIG. 10. The continuous electrodes162 can be substantially similar to the continuous electrodes 118 a-fshown and described in connection with FIGS. 3 and 4, while thesegmented electrode arrays 164 can be substantially similar to theplurality of segmented electrode arrays 120 a-e shown and described inconnection with FIGS. 3 and 4. Similar to the segmented electrode arrays120 a-e, the segmented electrode arrays 164 can include a plurality ofindividual electrodes 122 a-h. It is also noted that for the ease ofillustration every continuous electrode 162, segmented electrode array164, and individual electrode 122 a-h is not labelled in FIG. 10, butinstead a suitable representative number of elements are labelled.

The inlet section 152 and the outlet section 160 can each include, forexample, six rows of continuous electrodes 118 a-f and five segmentedelectrode arrays 165. However, it should be understood that more or lessrows and segmented electrode arrays can be included. The inlet section152 can be configured to receive ions from another section of the SLIMdevice 104, while the outlet section 160 can be configured to provideions to another section of the SLIM device 104. For example, the inletand outlet sections 152, 160 can be positioned adjacent to a transferregion 124, a separation region 128, a different accumulation region126, 150, or any other region of the SLIM device 104 so as to receiveions therefrom or provide ions thereto. Accordingly, the voltagesignals, e.g., the traveling wave voltage signal, applied to theindividual electrodes 122 a-h of the segmented electrode arrays 165 ofthe inlet section 152 and the outlet section 160 can be coordinated withthe voltage signals applied to the adjacent section of the SLIM device104 so that they are fully integrated and compatible. It should also beunderstood that the present disclosure contemplates at least oneembodiment in which the inlet section 152 can be additionally and/oralternatively implemented also as an outlet and the outlet section 160can be additionally and/or alternatively implemented as an inlet. Forexample, the ion accumulation section 156 could be implemented not onlyto accumulate ions, but also as a switching region that selectivelydirects ions to either the inlet section 152 (being utilized as anoutlet) or the outlet section 160.

The inlet transition section 154 extends from the inlet section 152 tothe ion accumulation section 156 and expands in width as it progressesalong the z-axis from the inlet section 152 to the ion accumulationsection 156. Accordingly, the width of the inlet transition section 154along the y-axis is greater at a position adjacent the ion accumulationsection 156 than it is at a position adjacent the inlet section 152.Additionally, the number of rows of continuous electrodes 162 andsegmented electrode arrays 164 gradually increases as the width of theinlet transition section 154 widens. Conversely, the outlet transitionsection 158 tapers and reduces in width as it progresses along thez-axis from the ion accumulation section 156 to the outlet section 160.Accordingly, the width of the outlet transition section 158 along they-axis is greater at a position adjacent the ion accumulation section156 than it is at a position adjacent the outlet section 160.Additionally, the number of rows of continuous electrodes 162 andsegmented electrode arrays 164 gradually decreases as the width of theoutlet transition section 158 reduces.

The accumulation region 150 is designed so that the ion accumulationsection 156 is wider, e.g., along the y-axis that is perpendicular tothe axis of ion propagation (the z-axis in FIG. 10), than the inletsection 152, the outlet section 160, and/or other portions of the paththrough the SLIM device 104. The accumulation region 150 is alsodesigned such that the inlet transition section 154 and the outlettransition section 158 provide a gradual transition between the inletand outlet sections 152, 160 and the accumulation section 156.Accordingly, the accumulation section 156 includes more rows ofelectrodes, e.g., rows of continuous electrodes 162 and segmentedelectrode arrays 164, than the other portions of the path through theSLIM device 104. For example, as shown in FIG. 10, the accumulationsection 156 can include sixteen rows of continuous electrodes 162 andfifteen segmented electrode arrays 164 while the inlet section 152 andthe outlet section 160, which are designed to interface with otherportions of the path through the SLIM device 104, include six rows ofcontinuous electrodes 162 and five segmented electrode arrays 164.

Additionally, the segmented electrode arrays 164 of the accumulationsection 156 can be divided into multiple groups or segments as describedin connection with FIG. 5. For example, each segmented electrode array164 of the accumulation section 156 can include three groups or segmentsof eight individual electrodes 122 a-h (e.g., twenty-four electrodes).The number of segmented electrode array groups and/or individualelectrodes 122 a-h per segmented electrode array group can be increasedor decreased depending on implementation and experimental needs.Additionally, the individual electrodes 122 a-h of the accumulationsection's 156 segmented electrode arrays 164 can receive a travelingwave signal independent from the transition sections 154, 158, the inletsection 152, and the outlet section 160, which allows for the travelingwave direction, and thus direction of ion travel through theaccumulation section 156, to be switched as needed. It should also beunderstood that the accumulation region 150 can be operated in the samefashion as shown and described in connection with FIGS. 6-8.

Moreover, each segmented electrode array 164 of the accumulation section156 can have one or more gate electrodes 166, e.g., the eighth electrode122 h of the third segmented electrode array group, that can have asignal applied thereto to trap or prevent the ions 132 a-c fromcontinued propagation through the accumulation region 150. Morespecifically, the gate electrodes 166 can receive a high DC voltagesignal from the controller 108 and in turn generate a high DC electricfield (V/m) to trap ions within the accumulation section 156 as they areprovided thereto by way of the inlet section 152, the inlet transitionsection 154, and the individual electrodes 122 a-h preceding the gateelectrodes 166. The accumulated ions are also retained laterally, e.g.,in the y-axis, by DC guard electrodes 168 that flank the sections152-160 of the accumulation region 150 and function in accordance withthe guard electrodes 116 shown and described in connection with FIGS. 3and 4. The expanded width of the accumulation section 156 allows it tohold more ions before encountering space charge issues compared to anarrower accumulation section, e.g., an accumulation section 156 that isthe same width as the inlet section 152 or the remainder of the paththrough the SLIM device 104.

Once a desired number of ions are accumulated in the accumulationsection 156, the high DC voltage signal can be removed and a travelingwave signal can be applied that is coordinated with the traveling wavesignal applied to the other individual electrodes 122 a-h within theaccumulation section 156, as well as with the traveling wave signalapplied to the outlet transition section 158. Once the high DC voltagesignal is removed and the traveling wave signal is applied, the ionswill be urged into the outlet transition section 158.

As previously noted, the outlet transition section 158 tapers from theion accumulation section 156 to the outlet section 160. For example, theoutlet transition section 158 shown in FIG. 10 narrows from thirty-onerows to eleven rows. This taper allows for ions to exit the accumulationsection 156 and transfer to the outlet section 160 while generallyavoiding reaching the space charge limit and being discharged due tospace charge effects. In this regard, faster ions, e.g., ions having agreater ion mobility, will exit the accumulation section 156 morequickly than slower ions causing the ions to separate as they traversethe outlet transition section 158. Accordingly, a larger area isnecessary immediately adjacent the gate electrodes 166 to accommodatethe cumulative charge of the released ions, which have not yet separatedat the beginning of the outlet transition section 158, and prevent theions from reaching the space charge limit. However, as the ions separatethe cumulative charge of the released ions at any given position alongthe length of the outlet transition section 158 will reduce, thusallowing the width of the outlet transition section 158 to be graduallyreduced to match the width of the outlet section 160. Additionally, theions are retained within the outlet transition section 158 and preventedfrom exiting laterally, e.g., along the y-axis, by the DC guardelectrodes 168. It should be understood that the length of the outlettransition section 158 and the slope of the taper thereof can beadjusted depending on the number of charges accumulated in the ionaccumulation region 156. For example, the outlet transition section 158shown in FIG. 10 has a length of sixteen individual electrodes 122 a-h,e.g., two groups of eight individual electrodes 122 a-h, but can beprovided as eight individual electrodes 122 a-h if such is determined tobe sufficient. The outlet section 160 receives the ions from the outlettransition section 158 and transfers the ions to another section of theSLIM device 104.

FIG. 11 is a schematic diagram of the exemplary accumulation region 150of FIG. 10 with a lateral inlet section 170 connected thereto.Specifically, in some aspects of the present disclosure, one or bothlateral sides of the ion accumulation section 156 can have an openingtherein with a lateral inlet section 170 positioned adjacent thereto.The lateral inlet section 170 can be substantially similar to the inletsection 152 and can include a plurality of columns of continuouselectrodes 162 and a plurality of segmented electrode arrays 164(oriented vertically along the y-axis instead of horizontally along thez-axis as in the inlet section 152) including a plurality of individualelectrodes 122 a-h. The lateral inlet section 170 is configured totransfer ions directly into the ion accumulation section 156.

The ion accumulation section 156 can be utilized to accumulate ionstherein and can function in accordance with the above descriptionprovided in connection with FIG. 10. In particular, the gate electrodes166 a, 166 b can receive a high DC voltage signal from the controller108 and in turn generate a high DC electric field (V/m) to trap ionswithin the accumulation section 156 as they are provided thereto by wayof the lateral inlet section 170. In this regard, the ion accumulationsection 156 can include two sets of gate electrodes 166 a, 166 b onopposite sides thereof providing a confinement zone there between.

Once a desired number of ions are accumulated in the accumulationsection 156 the ions can be transferred to either the outlet section 160or the inlet section 152, which could function as an outlet section solong as the appropriate traveling wave is applied thereto and to theinlet transition section 154. In particular, if ions are to be sent tothe outlet section 160, then the high DC voltage signal is removed fromthe right side gate electrodes 166 b and a traveling wave signal thattravels along the z-axis in the positive direction is applied to theindividual electrodes 122 a-h within the accumulation section 156 topush the ions into the outlet transition section 158 and subsequentlythe outlet section 160 where they can be provided to another pathsection of the SLIM device 104. Alternatively, if ions are to be sent tothe inlet section 152, then the high DC voltage signal is removed fromthe left side gate electrodes 166a and a traveling wave signal thattravels along the z-axis in the negative direction is applied to theindividual electrodes 122 a-h within the accumulation section 156, theinlet transition section 154 (functioning in similar fashion to theoutlet transition section 158), and the inlet section 152 (functioningin similar fashion to the outlet section 160) to push the ions into theinlet transition section 154 and subsequently the inlet section 152where they can be provided to another path section of the SLIM device104. Accordingly, the ion accumulation section 156 is independentlycontrollable and can be utilized to direct ions in different directions.Thus, the accumulation region 150 can be utilized not only to accumulateions, but also as a directional switch. It should also be understoodthat the accumulation region 150 could also be utilized as a directionalswitch without first accumulating ions.

Additionally, it should be understood that the transition sections 154,158 can be substantially similarly configured and sized, e.g., with thesame length and/or slope, or of different configurations and/or shapesas shown in FIG. 11. For example, the design of the transition sections154, 158 could be specifically tailored based on the desiredimplementation and the path section of the SLIM device 104 positionedsubsequent thereto.

Other embodiments are within the scope and spirit of the disclosedsubject matter. One or more examples of these embodiments areillustrated in the accompanying drawings. Those skilled in the art willunderstand that the systems, devices, and methods specifically describedherein and illustrated in the accompanying drawings are non-limitingexemplary embodiments and that the scope of the present disclosure isdefined solely by the claims. The features illustrated or described inconnection with one exemplary embodiment may be combined with thefeatures of other embodiments. Such modifications and variations areintended to be included within the scope of the present disclosure.Further, in the present disclosure, like-named components of theembodiments generally have similar features, and thus within aparticular embodiment each feature of each like-named component is notnecessarily fully elaborated upon.

The subject matter described herein can be implemented in digitalelectronic circuitry, or in computer software, firmware, or hardware,including the structural means disclosed in this specification andstructural equivalents thereof, or in combinations of them. The subjectmatter described herein can be implemented as one or more computerprogram products, such as one or more computer programs tangiblyembodied in an information carrier (e.g., in a machine-readable storagedevice), or embodied in a propagated signal, for execution by, or tocontrol the operation of, data processing apparatus (e.g., aprogrammable processor, a computer, or multiple computers). A computerprogram (also known as a program, software, software application, orcode) can be written in any form of programming language, includingcompiled or interpreted languages, and it can be deployed in any form,including as a stand-alone program or as a module, component,subroutine, or other unit suitable for use in a computing environment. Acomputer program does not necessarily correspond to a file. A programcan be stored in a portion of a file that holds other programs or data,in a single file dedicated to the program in question, or in multiplecoordinated files (e.g., files that store one or more modules,sub-programs, or portions of code). A computer program can be deployedto be executed on one computer or on multiple computers at one site ordistributed across multiple sites and interconnected by a communicationnetwork.

The processes and logic flows described in this specification, includingthe method steps of the subject matter described herein, can beperformed by one or more programmable processors executing one or morecomputer programs to perform functions of the subject matter describedherein by operating on input data and generating output. The processesand logic flows can also be performed by, and apparatus of the subjectmatter described herein can be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application-specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processor of any kind of digital computer. Generally, aprocessor can receive instructions and data from a read-only memory or arandom access memory or both. The essential elements of a computer are aprocessor for executing instructions and one or more memory devices forstoring instructions and data. Generally, a computer can also include,or be operatively coupled to receive data from or transfer data to, orboth, one or more mass storage devices for storing data, e.g., magnetic,magneto-optical disks, or optical disks. Information carriers suitablefor embodying computer program instructions and data include all formsof non-volatile memory, including by way of example semiconductor memorydevices, (e.g., EPROM, EEPROM, and flash memory devices); magneticdisks, (e.g., internal hard disks or removable disks); magneto-opticaldisks; and optical disks (e.g., CD and DVD disks). The processor and thememory can be supplemented by, or incorporated in, special purpose logiccircuitry.

To provide for interaction with a user, the subject matter describedherein can be implemented on a computer having a display device, e.g., aCRT (cathode ray tube) or LCD (liquid crystal display) monitor, fordisplaying information to the user and a keyboard and a pointing device,(e.g., a mouse or a trackball), by which the user can provide input tothe computer. Other kinds of devices can be used to provide forinteraction with a user as well. For example, feedback provided to theuser can be any form of sensory feedback, (e.g., visual feedback,auditory feedback, or tactile feedback), and input from the user can bereceived in any form, including acoustic, speech, or tactile input.

The techniques described herein can be implemented using one or moremodules. As used herein, the term “module” refers to computing software,firmware, hardware, and/or various combinations thereof. At a minimum,however, modules are not to be interpreted as software that is notimplemented on hardware, firmware, or recorded on a non-transitoryprocessor readable recordable storage medium (i.e., modules are notsoftware per se). Indeed “module” is to be interpreted to always includeat least some physical, non-transitory hardware such as a part of aprocessor or computer. Two different modules can share the same physicalhardware (e.g., two different modules can use the same processor andnetwork interface). The modules described herein can be combined,integrated, separated, and/or duplicated to support variousapplications. Also, a function described herein as being performed at aparticular module can be performed at one or more other modules and/orby one or more other devices instead of or in addition to the functionperformed at the particular module. Further, the modules can beimplemented across multiple devices and/or other components local orremote to one another. Additionally, the modules can be moved from onedevice and added to another device, and/or can be included in bothdevices.

The subject matter described herein can be implemented in a computingsystem that includes a back-end component (e.g., a data server), amiddleware component (e.g., an application server), or a front-endcomponent (e.g., a client computer having a graphical user interface ora web browser through which a user can interact with an implementationof the subject matter described herein), or any combination of suchback-end, middleware, and front-end components. The components of thesystem can be interconnected by any form or medium of digital datacommunication, e.g., a communication network. Examples of communicationnetworks include a local area network (“LAN”) and a wide area network(“WAN”), e.g., the Internet.

Approximating language, as used herein throughout the specification andclaims, may be applied to modify any quantitative representation thatcould permissibly vary without resulting in a change in the basicfunction to which it is related. Accordingly, a value modified by a termor terms, such as “about” and “substantially,” are not to be limited tothe precise value specified. In at least some instances, theapproximating language may correspond to the precision of an instrumentfor measuring the value. Here and throughout the specification andclaims, range limitations may be combined and/or interchanged, suchranges are identified and include all the sub-ranges contained thereinunless context or language indicates otherwise.

What is claimed is:
 1. An apparatus for ion accumulation, comprising: afirst region configured to receive ions and generate a first drivepotential configured to guide the ions across the first region in afirst direction; and a second region configured to receive the ions fromthe first region, switch between a first state and a second state,generate a first electric field when in the first state, and generate asecond electric field when in the second state; wherein the firstelectric field is configured to prevent the ions from moving in thefirst direction and entering a third region, and the second electricfield is configured to guide the ions in the first direction toward thethird region, and wherein when the second region is in the first statethe first drive potential and the first electric field prevent ions inthe second region from exiting the second region and causes the ions toaccumulate in the second region, and when the second region is in thesecond state the second electric field causes the ions to move in thefirst direction toward the third region.
 2. The apparatus of claim 1,wherein the first electric field is a DC voltage.
 3. The apparatus ofclaim 2, wherein a magnitude of the DC voltage is greater than a voltagebias of the first drive potential.
 4. The apparatus of claim 2, whereinthe second electric field is a traveling wave.
 5. The apparatus of claim2, wherein a magnitude of the DC voltage is less than a voltage bias ofthe first drive potential, the DC voltage creating a potential well. 6.The apparatus of claim 5, wherein the second electric field is a DCpotential gradient or a traveling wave.
 7. The apparatus of claim 2,wherein the first electric field is a traveling wave that travels in asecond direction that is opposite to the first direction, and the secondelectric field is a second traveling wave that travels in the firstdirection.
 8. The apparatus of claim 1, wherein the third region isconfigured to receive the ions from the second region and generate asecond drive potential configured to separate the ions based onmobility.
 9. The apparatus of claim 1, wherein the first region includesa plurality of electrodes disposed on a first surface, arranged alongthe first direction, and configured to generate the first drivepotential, and the second region includes one or more electrodesdisposed on the first surface, arranged along the first direction, andconfigured to generate the first electric field when in the first stateand generate the second electric field when in the second state.
 10. Theapparatus of claim 9, comprising: a controller configured to: apply afirst voltage signal to the plurality of electrodes of the first region,the plurality of electrodes configured to generate the first drivepotential based on the first voltage signal, apply a second voltagesignal to at least one electrode of the one or more electrodes of thesecond region, the at least one electrode configured to generate thefirst electric field based on the second voltage signal, and apply athird voltage signal to the at least one electrode of the one or moreelectrodes of the second region, the at least one electrode configuredto generate the second electric field based on the third voltage signal,wherein when the apparatus is in a first mode of operation thecontroller applies the second voltage signal to the second plurality ofelectrodes placing the second region in the first state, and when theapparatus is in a second mode of operation the controller applies thethird voltage signal to the second plurality of electrodes placing thesecond region in the second state.
 11. The apparatus of claim 1, whereina first portion of the second region generates the first electric fieldwhen the second region is in the first state, the first portion of thesecond region generates the second electric field when the second regionis in the second state, and a second portion of the second regiongenerates a fourth electric field that is different than the firstelectric field.
 12. The apparatus of claim 1, wherein the second regionincludes a plurality of rows of radio frequency (RF) electrodes and aplurality of traveling wave (TW) electrode arrays, each of the pluralityof TW electrode arrays including at least three individual electrodes.13. The apparatus of claim 12, wherein the first electric field isgenerated by at least one of the individual electrodes of each of theplurality of TW electrode arrays when the second region is in the firststate.
 14. A method of ion accumulation, comprising: introducing ionsinto an apparatus for ion accumulation having a first region, a secondregion, and a third region; generating a drive potential within thefirst region for guiding the ions across the first region in a firstdirection; transferring the ions from the first region to the secondregion with the drive potential; generating a first electric fieldwithin the second region for preventing the ions from moving in thefirst direction and entering the third region; accumulating ions in thesecond region; and switching the first electric field generated withinthe second region to a second electric field for guiding the accumulatedions in the first direction toward the third region.
 15. The method ofclaim 14, wherein the first electric field is a DC voltage.
 16. Themethod claim 15, wherein a magnitude of the DC voltage is greater than avoltage bias of the drive potential.
 17. The method of claim 15, whereinthe second electric field is a traveling wave.
 18. The method of claim15, wherein a magnitude of the DC voltage is less than a voltage bias ofthe drive potential, the DC voltage creating a potential well.
 19. Themethod of claim 18, wherein the second electric field is a DC potentialgradient or a traveling wave.
 20. The method of claim 15, wherein thefirst electric field is a first traveling wave that travels in a seconddirection that is opposite to the first direction, and the secondelectric field is a second traveling wave that travels in the firstdirection.
 21. The method of claim 14, further comprising: transferringthe ions accumulated in the second region to the third region;generating a second drive potential within the third region; andseparating the ions based on mobility with the second drive potential.22. The method of claim 14, wherein the first region includes aplurality of electrodes disposed on a first surface, arranged along thefirst direction, and configured to generate the first drive potential,the second region includes one or more electrodes disposed on the firstsurface and arranged along the first direction, and at least one of theone or more electrodes of the second region generates the first electricfield and the second electric field.
 23. The method of claim 14, whereina first portion of the second region generates the first electric fieldand the second electric field, and a second portion of the second regiongenerates a fourth electric field that is different than the firstelectric field.
 24. The method of claim 14, wherein the second regionincludes a plurality of rows of radio frequency (RF) electrodes and aplurality of traveling wave (TW) electrode arrays, each of the pluralityof TW electrode arrays including at least three individual electrodes.25. The method of claim 24, wherein the first electric field isgenerated by at least one of the individual electrodes of each of theplurality of TW electrode arrays when the second region is in the firststate.
 26. An ion accumulation device, comprising: an ion accumulationsection having a first width and being configured to receive ions,switch between a first state and a second state, generate a firstelectric field when in the first state, and generate a second electricfield when in the second state; an outlet section having a second widthless than the first width, the outlet section being configured togenerate a third electric field configured to guide the ions across theoutlet section; and an outlet transition section extending between theion accumulation section and the outlet section, and having a taperingwidth that reduces from the first width adjacent the ion accumulationsection to the second width adjacent the outlet section, the outlettransition section being configured to generate the third electric fieldto guide the ions across the outlet transition section to the outletsection; wherein the first electric field is configured to prevent theions from moving in a first direction and entering the outlet transitionsection, and the second electric field is configured to guide the ionsin the first direction toward the outlet transition section, and whereinwhen the ion accumulation section is in the first state the firstelectric field prevents ions in the ion accumulation section fromexiting the ion accumulation section and causes the ions to accumulatein the ion accumulation section, and when the ion accumulation sectionis in the second state the second electric field causes the ions to movein the first direction toward the outlet transition section.
 27. The ionaccumulation device of claim 26, comprising: an inlet section having athird width less than the first width; and an inlet transition sectionextending between the inlet section and the ion accumulation section,and having a tapering width that increases from the third width adjacentthe inlet section to the first width adjacent the ion accumulationsection, wherein the inlet section and the outlet transition section areconfigured to generate a fourth electric field to guide the ions acrossthe inlet section and the inlet transition section to the ionaccumulation section.
 28. The ion accumulation device of claim 26,wherein the second electric field is a traveling wave that travels inthe first direction, and the ion accumulation section is configured tobe switched from generating the second electric field to generating afourth electric field that is a traveling wave that travels in a seconddirection opposite the first direction.
 29. The ion accumulation deviceof claim 26, wherein the first electric field is a DC voltage.
 30. Theion accumulation device of claim 26, wherein a first portion of the ionaccumulation section generates the first electric field and a secondportion of the ion accumulation section generates a fourth electricfield that is different than the first electric field.
 31. The ionaccumulation device of claim 26, wherein the ion accumulation sectionincludes a plurality of rows of radio frequency (RF) electrodes and aplurality of traveling wave (TW) electrode arrays, each of the pluralityof TW electrode arrays including at least three individual electrodes.32. The ion accumulation device of claim 31, wherein the first electricfield is generated by at least one of the individual electrodes of eachof the plurality of TW electrode arrays.
 33. The ion accumulation deviceof claim 26, comprising an inlet section positioned at a lateral side ofthe ion accumulation section and configured to provide ions to the ionaccumulation section.